The present invention generally relates to a sample vessel and, in particular, relates to such a vessel which includes means for simultaneously controlling both the sealing thereof and the delivery of a sample therefrom. In a preferred embodiment the vessel is adapted for use in conjunction with an ultra-high vacuum analytical instrument.
As the techniques for analytically determining the elemental and/or chemical nature of sample surfaces develop, the purity requirement of samples, or specimens, to be tested also increases. One such analytical technique is generally known as ESCA (Electron Spectroscopy for Chemical Analysis). In an ESCA instrument, the surface of a sample is bombarded with soft X-rays which liberate photoelectrons from the sample surface. All elements, with the exception of hydrogen, which are present in detectable amounts within the X-ray absorption volume generate well defined peaks in the photoelectron energy distribution. The elemental or chemical composition of the surface is then determined from the peaks in the energy distribution. The ESCA technique provides quite accurate surface information and, because of its sensitivity, it is imperative that the surface undergoing analysis be as free as possible from any contaminants or contamination. As used herein the word "surface" refers to the first few atomic layers of the sample undergoing analysis.
Generally, in order to have an ESCA examination of a specimen the specimen is isolated, or prepared, and mounted on a specimen holder remote from the instrument. The prepared specimen is then placed in a sample vessel for transport to a laboratory whereat it is inserted into an ESCA instrument and the analysis is performed.
Almost any sample to be analyzed is susceptible to some form of contamination right from the moment it is isolated from its source and continues to be susceptible until it is placed in the ultra-high vacuum environment of the analytical instrument. Ideally, of course, a sample is isolated in close physical proximity with the instrument. However, such convenient physical proximity is rarely available in the practical world. This condition exists for a number of obvious reasons, not the least of which is the considerable expense of the analytical instrument itself in addition to the relatively small number of trained instrument operators. Consequently, samples which are to be analyzed are usually required to be transported over substantial distances and times after they are isolated. One conventional precaution used when isolating highly contaminative specimens, is the use of a "glove box". By use of such a device the sample is isolated and packaged in an inert atmosphere. When the sample is removed from the shipping package and inserted into the instrument, the entire entry chamber must be evacuated to an ultra-high vacuum level prior to exposing the packaged sample thereto. Such a procedure is not only time consuming, since the creation of an ultra-high vacuum within an analytical instrument takes a considerable amount of time, but also exposes the sample to be tested to a potentially contaminating atmosphere until the ultra-high vacuum is achieved. Further, once the entry chamber reaches an ultra-high vacuum level and the vessel is opened, the ultra-high vacuum is lost due to the atmosphere within the vessel and, hence, must be reestablished.
Nevertheless, such precautionary procedures are unacceptable when the sample is a chemically active element, i.e., one which can be easily contaminated by the least exposure to any environment or an element which can be hazardous, i.e., explosive, when exposed to such an ambient. Sample vessels for transporting such specimens are known in the art wherein the vessel itself can be inserted into the ultra-high vacuum system and maintained in that position prior to exposing the sample thereto.
One such vessel is described in U.S. Pat. Ser. No. 259,723, filed May 1, 1981, now U.S. Pat. No. 4,411,575 and assigned to the assignee hereof. As described therein, a vessel includes a sample mounting block upon which a sample holder can be secured. The device includes a lid into which the mounting block can be placed and hermetically sealed.
In use, one end of the vessel is inserted into an instrument entry chamber wherein the mounting block is removed, together with the specimen carried thereon, which specimen is then removed by a forked sample receiving mechanism. Although such a device performs quite well for the purpose intended, it inherently is somewhat disadvantageous in that the atmosphere within the vessel itself is merely inert and is not capable of being provided with an ultra-high vacuum. This is disadvantageous primarily because of the length of time necessary to reduce even an entry chamber to an ultra-high vacuum level after the vessel is opened. That is, pumping must usually be continued to remove the inert gases within the vessel.
Other vessels are available which remotely control the opening of the vessel once inside the ultra-high vaccum chamber by a mechanism integral with the vessel itself. Such vessels require multiple controls i.e., a first control for the opening and closing thereof and a second control, also integrated within the vessel, for transporting the sample into, or out of, the vessel proper. Such a sample transfer vessel is cumbersome to operate and subject to failures due to the multiplicity of control related moving parts therein.
From the above, it is quite clear that there is a considerable need for an easily operated sample vessel within which a sample can be transported under an ultra-high vacuum.